Method and apparatus for controlling rate of pressure change in a vacuum process chamber

ABSTRACT

A method, apparatus and system for controlling a rate of pressure change in a vacuum process chamber during pump down and vent up cycles of a vacuum process are provided. The method includes sensing the pressure in the process chamber, and then controlling the rate of pressure change to achieve a desired rate for a particular vacuum process. For a pump down cycle, the apparatus can include a control valve in flow communication with the process chamber and with an evacuation pump. For a vent up cycle, the apparatus can include a control valve in flow communication with the process chamber and with an inert gas supply. With either embodiment controllers can be programmed to adjust positions of the control valves based upon feedback from pressure sensors. The system can include multiple chambers each having an associated pump down and vent up control apparatus configured to match the rates of pressure change between chambers.

FIELD OF THE INVENTION

[0001] This invention relates generally to vacuum processes, such as dryetching and chemical vapor deposition particularly for semiconductormanufacture. More specifically, this invention relates to a method andapparatus for controlling a rate of pressure change in a vacuum processchamber during pump down and vent up cycles of a vacuum process.

BACKGROUND OF THE INVENTION

[0002] Various etching and deposition processes for semiconductormanufacture are performed in vacuum process chambers. For example, dryetching and chemical vapor deposition (CVD) processes utilize vacuumprocess chambers. Conventional dry etching processes include plasmaetching and reactive ion etching (RIE). Conventional chemical vapordeposition processes include plasma enhanced chemical vapor deposition(PECVD) and low pressure chemical vapor deposition (LPCVD).

[0003] During these processes the process chamber can be evacuated froman initial pressure to an operating pressure. For example, the processchamber may initially be at atmospheric pressure for loading wafers,then evacuated to an operational pressure in the milli-torr range. Theinitial evacuation cycle for a process is sometimes referred to as a“pump down cycle”. Typically, a pump down cycle is accomplished using avacuum pump in flow communication with the process chamber.

[0004] Subsequently, the pressure in the process chamber can beincreased from the operating pressure back to the initial pressure(e.g., back to atmospheric pressure). The subsequent pressurizationcycle is sometimes referred to as a “vent up cycle”. Typically, a ventup cycle is accomplished by injecting an inert gas into the processchamber to a desired pressure.

[0005] Recently, etching and deposition systems having more than onevacuum process chamber have been employed for semiconductor manufacture.These multi-chamber systems improve production rates and provideincreased efficiency over single chamber systems. An example of amulti-chambered etching or deposition system is sold under the trademark“APPLIED MATERIALS 5000”, by Applied Materials, Inc., of Santa Clara,Calif.

[0006] Such a multi chambered system can include a wafer handler, a loadlock chamber and multiple process chambers. The wafer handler caninclude cassettes for holding the wafers and cassette ports for loadingthe wafers. During an etching or deposition process, the wafers can bemoved from the load lock chamber and into or out of the process chambersas required. The process chambers can be pumped down and vented up todifferent pressures during various cycles of the process.

[0007] One limitation of multi chamber systems is that wafer defects cansometimes occur more frequently in a particular process chamber relativeto the other process chambers. For example, some types of wafer defectscan be detected using optical detectors such as those manufactured byKLA Instruments Corporation, Santa Clara, Calif. These types of defectsare sometimes termed “KLA defects”. The inventors have observedvariations in KLA defects among wafers processed in different processchambers of multi chamber vacuum systems. In particular, some processchambers in multi chamber systems produce wafers with more defects.

[0008] One possible source of defect variation between the processchambers is that the rate of pressure change for the chambers duringpump down and vent up cycles may not be the same. This difference inrate of pressure change can cause the pressures in the process chambersto be different for significant time increments. The pressure ratedifferences may be due to variations between conduction lines, pumps,valves and associated equipment for the different chambers. Thesevariations can be caused by residue build up and other factors.

[0009] The same situation can occur among different single chambersystems adapted to perform the same process. Specifically, variationscan occur between the different process chambers causing differences inthe wafers. In this situation it would be advantageous to control therate of pressure change during pump down and vent up in the processchambers in order to achieve process uniformity.

[0010] Prior art attempts to regulate pump down cycles in vacuum processchambers include “soft-start” valves, which open at a linear rate (i.e.,at a certain percentage per second). Prior art attempts to regulate ventup cycles in vacuum process chambers include needle valves and mass flowcontrollers which control the flow rate into a particular chamber duringvent up. However, these prior art systems do not compensate for systemvariables and are inherently linear in response. Accordingly,significant pressure differentials can still occur between differentprocess chambers causing differences in the semiconductor wafers beingprocessed.

[0011] The present invention provides a method and apparatus forachieving an optimal rate of pressure change in a vacuum process chamberduring pump down and vent up cycles of a vacuum process. For multichamber vacuum systems, the rate of pressure change between differentprocess chambers can be matched such that one process variable can beeliminated and wafer uniformity can be improved. Similarly, for multiplesingle chamber systems adapted to perform the same process, one processvariable can be eliminated and the uniformity of the wafers produced bythe different vacuum process chambers can be improved.

SUMMARY OF THE INVENTION

[0012] In accordance with the present invention, a method and apparatusfor controlling the rate of pressure change in a process chamber duringpump down and vent up cycles of a vacuum process are provided. Themethod, simply stated, comprises, determining a desired rate of pressurechange for the process chamber, and then, controlling the gas flow outof, or into, the process chamber to achieve the desired rate of pressurechange. The gas flow can be controlled using a flow control valve andprogrammed controller responsive to feed back from pressure sensorswithin the process chamber. The desired rate of pressure change can bedetermined empirically for a particular vacuum process, expressedmathematically, and then programmed into the controller.

[0013] An apparatus constructed in accordance with the invention,comprises: a pressure sensor for sensing pressure in the processchamber; a control valve in flow communication with the process chamber;and a programmed controller for controlling the control valve responsiveto the pressure sensor. Separate controllers and control valves can beoperably associated with the process chamber for the pump down and ventup cycles of a vacuum process. For controlling the pump down cycle, acontrol valve can be in flow communication with a vacuum pump. Forcontrolling the vent up cycle, a control valve can be in flowcommunication with an inert gas supply.

[0014] A system constructed in accordance with the invention comprisesmultiple process chambers configured for a vacuum process such asdepositing or etching layers of semiconductor wafers. The multipleprocess chamber can be contained on the same frame or can be containedon separate pieces of equipment configured to perform the same process.Each process chamber includes a pressure sensor, and separate controlvalves and controllers for controlling pump down and vent up cyclesduring the vacuum processes. The controllers and control valves can beconfigured to match the rates of pressure change in the process chambersduring the pump down and vent up cycles. The matched rates permit moreprocess uniformity between the process chambers so that excessivedefects do not occur in any one process chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1A is a flow diagram of a method for controlling a rate ofpressure change in a vacuum process chamber during a pump down cycle ofa vacuum process;

[0016]FIG. 1B is a flow diagram of a method for controlling a rate ofpressure change in a vacuum process chamber during a vent up cycle of avacuum process;

[0017]FIG. 2A is a schematic diagram of an apparatus constructed inaccordance with the invention for controlling the rate of pressurechange in a vacuum process chamber during a pump down cycle of a vacuumprocesses;

[0018]FIG. 2B is a schematic diagram of an apparatus constructed inaccordance with the invention for controlling the rate of pressurechange in a vacuum process chamber during a vent up cycle of a vacuumprocess;

[0019]FIG. 2C is a graph illustrating the pressure within the vacuumprocess chamber as a function of time during pump down, operational andvent up cycles of a vacuum process;

[0020]FIG. 3A is a schematic diagram of a multi chambered systemconstructed in accordance with the invention with multiple processchambers contained on a same frame, wherein the rate of pressure changein the different process chambers during pump down and vent up can bematched;

[0021]FIG. 3B is a schematic diagram of a multi chambered systemconstructed in accordance with the invention with multiple processchambers on separate pieces of equipment but configured to perform thesame process, wherein the rate of pressure change in the differentprocess chambers during pump down and vent up can be matched;

[0022]FIG. 4 is a graph of pressure vs. time in a process chamber duringa pump down cycle illustrating a rate of pressure change comprising aseries of linear segments;

[0023]FIG. 5 is a graph of pressure vs. time in a process chamber duringa pump down cycle illustrating another rate of pressure changecomprising a series of linear segments; and

[0024]FIG. 6 is a graph of pressure vs. time in a process chamber duringa vent up cycle illustrating a rate of pressure change comprising anexponential curve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Referring to FIG. 1A, broad steps in a method for controlling therate of pressure change in a vacuum process chamber during a pump downcycle of an etching or deposition process are shown. For a pump downcycle the method includes the steps of:

[0026] A. Providing a vacuum process chamber in flow communication witha vacuum pump.

[0027] B. Providing an evacuation control valve in flow communicationwith the process chamber and with the vacuum pump.

[0028] C. Providing a controller for controlling the evacuation controlvalve.

[0029] D. Providing a pressure sensor in the process chamber inelectrical communication with the controller.

[0030] E. Sensing a pressure in the process chamber using the pressuresensor.

[0031] F. Controlling the rate of pressure change by inputting signalsfrom the pressure sensor to the controller to control a flow ratethrough the control valve out of the chamber.

[0032] Referring to FIG. 1B, broad steps in a method for controlling therate of pressure change in a vacuum process chamber during a vent upcycle are shown. For a vent up cycle the method includes the steps of:

[0033] A. Providing a vacuum process chamber in flow communication witha vent source such as an inert gas supply.

[0034] B. Providing a vent control valve in flow communication with theprocess chamber and vent source.

[0035] C. Providing a controller for controlling the vent control valve.

[0036] D. Providing a pressure sensor in the process chamber inelectrical communication with the controller.

[0037] E. Sensing a pressure in the process chamber using the pressuresensor.

[0038] F. Controlling the rate of pressure change by inputting signalsfrom the pressure sensor to the controller to control a flow rate fromthe vent source through the control valve into the chamber.

[0039] Referring to FIG. 2A, a pump down apparatus 10P for controlling arate of pressure change in a vacuum process chamber 12 during a pumpdown cycle is illustrated. The pump down apparatus 10P includes apressure sensor 14P configured to sense a pressure within the processchamber; a controller 16P in electrical communication with the pressuresensor 14P configured to receive feedback from the pressure sensor 14P;and a pump down control valve 18P coupled to the controller 16P in flowcommunication with the process chamber 12.

[0040] The vacuum process chamber 12 can be a component of an etchingsystem such as a plasma etcher or a reactive ion etcher (RIE).Alternately the vacuum process chamber 12 can be a component of a CVDdeposition system such as a plasma enhanced chemical vapor deposition(PECVD) apparatus, or a low pressure chemical vapor deposition (LPCVD)reactor.

[0041] The vacuum process chamber 12 is adapted to contain a gaseousetching or deposition species. The vacuum process chamber 12 is in flowcommunication with an evacuation pump 20. The evacuation pump 20 isconfigured to pump down (i.e., evacuate) and then to maintain theprocess chamber 12 at a desired vacuum pressure. For vacuum etching ordeposition processes, the vacuum process chamber 12 can be evacuated topressures of from 760 torr to 10⁻⁸ torr or less. Suitable conduits, suchas tubes or pipes, can be formed between the vacuum process chamber 12and the evacuation pump 20 to form conduction lines for the etching ordeposition gases.

[0042] The pump down control valve 18P is located in the flow path ofthe etching or deposition gases from the process chamber 12 to theevacuation pump 20. The pump down control valve 18P is configured toregulate a flow rate of gases from the vacuum process chamber 12 to theevacuation pump 20 during a pump down cycle. The pump down control valve18P can be a standard flow control valve such as a throttle valve orbutterfly valve that is responsive to electrical signals from thecontroller 16P.

[0043] The controller 16P is configured to receive electrical signalsfrom the pressure sensor 14P. This provides real time feed back to thecontroller 16P of the pressure within the process chamber 12. Inaddition, the controller 16P is configured to input electrical signalsinto the pump down control valve 18P for adjusting the pump down controlvalve 18P to achieve a desired flow rate at a particular pressure.

[0044] The controller 16P can include a microprocessor and programmablememory that is programmable to achieve a desired mode of operation forthe controller 16P. For example, the controller 16P can be programmedsuch that the pump down control valve 18P achieves a desired rate ofpressure change in the process chamber 12 during the pump down cycle.The controller 16P can also include a calibration cycle wherein the rateof pressure change at a given pressure versus a valve position for thecontrol valve 18P at that pressure is determined. The calibration stepis optional but makes the response of the control valve 18P more rapidand accurate.

[0045] As will be further explained, the desired rate of pressure changecan be an empirically determined optimal rate. In addition, for multiplechamber systems, the desired rate of pressure change can be matched tothe rate in another chamber. The multiple chambers can be included inthe same system, or frame, or can be included in separate systemsadapted to perform the same process.

[0046] Preferably, the desired rate of pressure change can be expressedmathematically such as illustrated in FIGS. 4-6. In these figures,pressure is plotted as a function of time and the rate of pressurechange AP comprises the slope of the resultant curve.

[0047] Referring to FIG. 2B, a vent up apparatus 10V for controlling arate of pressure change in the process chamber 12 during a vent up cycleof a vacuum process is shown. During the vent up cycle the pressurewithin the process chamber 12 can be increased to a level that is higherthan the operating pressure for a particular vacuum process. Thisincreased pressure level can be atmospheric pressure, or can be anintermediate pressure level, such as the vacuum pressure of a load lockchamber for the process chamber 12.

[0048] The vent up apparatus 10V comprises a pressure sensor 14Vconfigured to sense a pressure within the process chamber; a controller16V in electrical communication with the pressure sensor 14V configuredto receive feedback from the pressure sensor 14V; and a vent up flowcontrol valve 18V coupled to the controller 16V in flow communicationwith the process chamber 12.

[0049] In the vent up apparatus 10V, the vacuum process chamber 12 is inflow communication with an inert gas supply 28. The inert gas supply 28can be maintained at a higher pressure than the operating pressure ofthe process chamber 12. The inert gas supply 28 is configured to injectan inert gas into the process chamber 12 during the vent up cycle. Thevent up control valve 18V is configured to regulate a flow rate of gasfrom the inert gas supply 28 to the vacuum process chamber 12 during thevent up cycle. The controller 16V can be constructed as previouslydescribed for controller 16P and can include a microprocessor andprogrammable memory. Feed back from the pressure sensor 14V to thecontroller 16V enables the controller 16V to adjust the positions of thevent up control valve 18V to achieve a desired gas flow and rate ofpressure change during the vent up cycle. Again this desired rate ofpressure change can be empirically determined and can be matched in amulti chamber system. In addition, the controller 16V can include aperiodic calibration cycle to determine the rate of pressure change at agiven pressure and valve position.

[0050]FIG. 2C illustrates the pressure in the process chamber 12 as afunction of time during an etching or deposition process. During thepump down cycle, the pressure in the process chamber 12 is decreased asindicated by the pump down portion 22 of the pressure curve. The rate ofpressure change (ΔP) during the pump down cycle (i.e., slope of portion22) is controlled by the controller 16P (FIG. 2A) and the pump downcontrol valve 18P (FIG. 2A). During the operating cycle, the pressure inthe process chamber 12 is maintained at a desired operating pressure asindicated by the operating portion 24 of the pressure curve. During thevent up cycle, the pressure in the process chamber 12 is increased asindicated by the vent up portion 26 of the pressure curve. During thevent up cycle, the rate of pressure change (ΔP) is controlled by thecontroller 16V (FIG. 2B) and vent up control valve 18V.

[0051] Referring to FIG. 3A, a multi chamber system 30A constructed inaccordance with the invention with multiple chambers on a same frame isshown. As used herein, the term “same frame” refers to a single piece ofequipment. For example, the system 30A can be based on a commerciallyavailable multi chamber frame, such as an “APPLIED MATERIALS 5000”manufactured by Applied Materials, Inc. of Santa Clara, Calif.

[0052] The system 30A can be configured for etching or depositing layerson semiconductor wafers during semiconductor fabrication processes. Thesystem 30A includes a first process chamber 12A, a second processchamber 12B, and a third process chamber 12C. The system 30A can alsoinclude a wafer handler 32 configured to transport semiconductor wafersloaded in cassettes from a load lock station into the process chambers12A-12C for etching or deposition processes.

[0053] Each process chamber 12A-12C includes an associated pump downapparatus 10PA-10PC. Each pump down apparatus 10PA-10PC includes a pumpdown pressure sensor 14PA-14PC, a pump down controller 16PA-16PC, a pumpdown control valve 18PA-18PC, and an evacuation pump 20A-20C. Theseelements function the same as the equivalent elements previouslydescribed. In the multi chamber system 30A, the rate of pressure changein the different process chambers 12A-12C during the pump down cycle canbe an optimal rate as previously described. In addition, the rate ofpressure change (ΔP) can be substantially the same (i.e., matched) foreach process chamber 12A-12C.

[0054] Each process chamber 12A-12C also includes an associated vent upapparatus 10VA-10VC. Each vent up apparatus 10VA-10VC includes a vent uppressure sensor 14VA-14VC, a vent up controller 16VA-16VC, a vent upcontrol valve 18VA-18VC, and an inert gas supply 28A-28C. These elementsfunction the same as the equivalent elements previously described. Inthe multi chamber system 30A, the rate of pressure change (ΔP) in thedifferent process chambers 12A-12C during the vent up cycle can be anoptimal rate as previously described. In addition, the rate of pressurechange can be substantially the same (i.e., matched) for each processchamber 12A-12C.

[0055] Referring to FIG. 3B, a system 30B includes separate processchambers 12D-12F that are not contained on the same frame. For example,the process chambers 12D-12F can be similar pieces of equipment that arenot clustered together, but which perform the same processes (e.g.,polysilicon deposition, metal etching, silicon nitride deposition andetching etc.). Since these process chambers 12D-12F may be in differentareas of the semiconductor manufacturing plant, process variables canoccur between the process chambers 12D-12F. For example, these processvariables can include differences in pumping speeds, conduction lineresistance, preventative maintenance schedules as well as others.

[0056] In accordance with the invention, each process chamber includesan associated vent up apparatus 10VD-10VF. Each vent up apparatus10VD-10VF includes a vent up pressure sensor 14VD-14VF, a vent upcontroller 16VD-16VF, a vent up control valve 18VD-18VF, and an inertgas supply 28D-28F. These elements function the same as the equivalentelements previously described. In the multi chamber system 30B the rateof pressure change (ΔP) in the different process chambers 12D-12F duringthe vent up cycle can be an optimal rate as previously described. Inaddition, the rate of pressure change can be substantially the same(i.e., matched) for each process chamber 12D-12F.

[0057] As also shown in FIG. 3B, each process chamber 12D-12F includesan associated pump down apparatus 10PD-10PF. Each pump down apparatus10PD-10PF includes a pump down pressure sensor 14PD-14PF, a pump downcontroller 16PD-16PF, a pump down control valve 18PD-18PF, and anevacuation pump 20D-20F. These elements function the same as theequivalent elements previously described. In the multi chamber system30B, the rate of pressure change in the different process chambers12D-12F during the pump down cycle can be an optimal rate as previouslydescribed. In addition, the rate of pressure change (ΔP) can besubstantially the same value (i.e., matched) for each process chamber12D-12F.

[0058] In the multi chamber system 30B shown in FIG. 3B, each of theprocess chambers 12D-12F can be configured to perform the same processor “recipe”. In addition, the vent up and pump down cycles for eachrecipe can be matched. Still further, the process chambers 12D-12F cancomprise stock equipment from different equipment vendors but still usethe same pump down and vent up cycles for a given process recipe.

EXAMPLE 1

[0059] Referring to FIG. 4, an exemplary pump down cycle for the pumpdown apparatus 10P (FIG. 2) is shown. In FIG. 4, the pressure in theprocess chamber 12 (FIG. 2) is plotted as a function of time as the pumpdown cycle progresses. Initially, the process chamber 12 (FIG. 2) has apressure of approximately 760 torr. An optimal rate of pressure dropduring the pump down cycle includes three (pressure v time) segments.

[0060] In a first segment the pressure is to be reduced to 100 torr in20 seconds. In a second segment the pressure is to be reduced from 100torr to 1 torr in 15 seconds. In a third segment the pressure is to bereduced from 1 torr to 500 milli-torr in 15 seconds. The rate ofpressure change during each segment is represented by ΔP1, ΔP2 and ΔP3.Each rate of pressure change for a respective segment is linear for thatsegment. In other words, the change in pressure for each segment isdirectly proportional to the change in time. However, the rate of changeΔP1, ΔP2 and ΔP3 is different for each segment.

[0061] The (pressure vs. time) segments can be empirically determinedand then programmed into the controller 16P (FIG. 2A). During eachpressure segment the controller 16P (FIG. 2A) based upon input from thepressure sensor 14P (FIG. 2A) adjusts the position of the pump downcontrol valve 18P (FIG. 2) to meet the desired rate of pressure change.

EXAMPLE 2

[0062] Referring to FIG. 5, another example of a pump down cycle isillustrated. In this example the process chamber 12 (FIG. 2A) isadjacent to a staging area, such as a load lock, wherein transfer of thewafers into the process chamber 12 (FIG. 2A) takes place. The stagingarea is at a pressure that is less than atmosphere, which in thisexample is 10 torr. On the other hand, the desired steady stateprocessing pressure in the process chamber (FIG. 2A) is to be 150milli-torr.

[0063] It is desired to pump down in a linear fashion from 10 torr to 1torr in ten seconds, then from 1 torr to 500 millitorr in 15 seconds,then from 500 milli-torr to the operating pressure of 150 milli torr in20 seconds. These rates of pressure change are represented by segments4, 5 and 6 respectively. Segment 7 represents the steady state operatingpressure.

[0064] Based upon these predetermined rates of pressure change, thecontroller 16P (FIG. 2A) can be programmed to adjust the positions ofthe pump down control valve 18P (FIG. 2A) responsive to input from thepressure sensor 14P (FIG. 2A) to achieve the desired rate. Prior to thepump down cycle, a calibration cycle can be performed to determine therate of pressure drop at a given pressure for different positions of thecontrol valve 18P.

EXAMPLE 3

[0065] Referring to FIG. 6, an exemplary vent up cycle is illustrated.During the vent up cycle the pressure in the process chamber 12 (FIG.2B) is increased from a steady state operating pressure 34 toatmospheric pressure. In this case it is desired to increase thepressure in the process chamber 12 (FIG. 2B) in a non linear orexponential manner. An exponential curve 36 represents the desired rateof pressure change during the vent up cycle. The exponential curve 36can be empirically determined.

[0066] In accordance with the invention, the vent up controller 16V(FIG. 2B) is programmed to achieve a rate of pressure change in theprocess chamber 12 (FIG. 2B) that is equivalent to the exponential curve36. Accordingly, the vent up controller 16V (FIG. 2B) based uponfeedback from the pressure sensor 14V, (FIG. 2B) adjusts the positionsof the vent up control valve 18V (FIG. 2B). The vent up control valve18V meters the flow of inert gas from the inert gas supply 28 (FIG. 2B)to achieve the desired rate of pressure change.

[0067] Thus the invention provides an improved method, apparatus andsystem for controlling the rate of pressure change in a vacuum processchamber during pump down and vent up cycles of a vacuum etching ordeposition process. In addition, the invention permits an optimal rateof pressure change to be achieved in a single chamber or multi chamberetching or deposition system. For a multi chamber system the rate ofpressure change between different chambers of the system can be madesubstantially the same. This improves process uniformity because atleast one variable is eliminated, and permits semiconductor wafers to befabricated with fewer defects.

[0068] While the invention has been described with reference to certainpreferred embodiments, as will be apparent to those skilled in the art,certain changes and modifications can be made without departing from thescope of the invention as defined by the following claims.

What is claimed is:
 1. A method for controlling a rate of pressurechange in a vacuum process chamber during a vacuum process comprising:determining a desired rate of pressure change for the chamber during thevacuum process; providing a valve in flow communication with thechamber; sensing a pressure within the chamber; and controlling a flowthrough the valve responsive to the pressure to achieve the desired rateof pressure change.
 2. The method as claimed in claim 1 and wherein thevacuum process comprises an etching process.
 3. The method as claimed inclaim 1 and wherein the vacuum process comprises a deposition process.4. A method for controlling a rate of pressure change during a pump downcycle for a vacuum process chamber comprising: determining a desiredrate of pressure change for the chamber during the pump down cycle;providing a valve in flow communication with the chamber and with apump; and controlling a flow through the valve to the pump by sensingpressure in the chamber and adjusting a position of the valve responsiveto the pressure to achieve the desired rate of pressure change.
 5. Themethod as claimed in claim 4 wherein adjusting the position of the valveis performed with a controller.
 6. The method as claimed in claim 5wherein the controller is programmable to store the desired rate ofpressure change.
 7. A method for controlling a rate of pressure changeduring a vent up cycle for a vacuum process chamber comprising:determining a desired rate of pressure change for the chamber during thevent up cycle; providing a valve in flow communication with the chamberand with a gas supply; and controlling a flow through the valve to thechamber by sensing pressure in the chamber and adjusting a position ofthe valve responsive to the pressure to achieve the desired rate ofpressure change.
 8. The method as claimed in claim 7 wherein adjustingthe position of the valve is performed with a controller.
 9. The methodas claimed in claim 8 wherein the controller is programmable to storethe desired rate of pressure change.
 10. A method for controlling a rateof pressure change in a process chamber during a vacuum processcomprising: providing a pressure sensor in the chamber; providing avalve in flow communication with the chamber; providing a programmedcontroller in electrical communication with the pressure sensorconfigured to adjust a flow rate through the valve responsive to signalsfrom the pressure sensor; sensing a pressure in the chamber andcommunicating the pressure to the controller; and controlling a flowrate through the valve such that the rate of pressure change in thechamber matches a desired rate of pressure change programmed into thecontroller.
 11. The method as claimed in claim 10 wherein the methodcontrols the rate of pressure change during a pump down cycle for thevacuum process.
 12. The method as claimed in claim 10 wherein the methodcontrols the rate of pressure change during a vent up cycle for thevacuum process.
 13. A method for controlling a vacuum processcomprising: providing a plurality of vacuum process chambers; providinga plurality of valves in flow communication with the chambers; providingat least one controller for the valves configured to control flow ratesthrough the valves; providing a plurality of pressure sensors in thechambers in electrical communication with the controller; and matchingrates of pressure change in the chambers by controlling flow ratesthrough the valves using the controller and feedback from the pressuresensors.
 14. The method as claimed in claim 13 and further comprisingproviding the controller with desired rates of pressure change andmatching the rates of pressure change to the desired rates of pressurechange.
 15. The method as claimed in claim 13 wherein the vacuum processcomprises an etching process or a deposition process.
 16. A method forcontrolling a plurality of vacuum process chambers comprising: providinga pressure sensor in each chamber; providing a plurality of controlvalves for controlling flow rates into and out of each chamber;providing a plurality of controllers for the control valves, with eachcontroller in electrical communication with a respective pressure sensorand valve; programming each controller with a desired rate of pressurechange; and adjusting the flow rate through the valves using thecontrollers and pressure sensors, such that a rate of pressure change ineach chamber matches the desired rate of pressure change.
 17. The methodas claimed in claim 16 wherein the desired rate of pressure change isfor a pump down cycle of a vacuum process.
 18. The method as claimed inclaim 16 wherein the desired rate of pressure change is for a vent upcycle of a vacuum process.
 19. The method as claimed in claim 16 whereinthe vacuum process chambers are contained on a same frame.
 20. Themethod as claimed in claim 16 wherein the vacuum process chambers arecontained on separate pieces of equipment.
 21. A method for controllinga vacuum process during processing o f a semiconductor wafer comprising:providing a vacuum process chamber; determining a desired rate ofpressure change in the chamber during the vacuum process; sensing apressure in the chamber; providing a valve in gaseous flow communicationwith the chamber; and controlling a gas flow through the valve byadjusting a position of the valve responsive to sensing the pressure, tosubstantially match the rate of pressure change in the chamber duringthe vacuum process with the desired rate of pressure change.
 22. Themethod as claimed in claim 21 wherein the vacuum process comprises anetching process.
 23. The method as claimed in claim 21 wherein thevacuum process comprises a deposition process.
 24. An apparatus forcontrolling a rate of pressure change in a vacuum process chamber duringa pump down cycle of a vacuum process comprising: a pressure sensorconfigured to sense a pressure within the chamber; a control valve inflow communication with the chamber and with a pump; and a controllerfor the control valve in electrical communication with the sensor, saidcontroller configured to control flow from the chamber through thecontrol valve to the pump, said controller responsive to input from thesensor to achieve a desired rate of pressure change in the chamber. 25.The apparatus as claimed in claim 24 wherein the controller comprises aprogrammable memory wherein the desired rate of pressure change isstored.
 26. The apparatus as claimed in claim 24 wherein the chamber iscontained in a multi chambered system and the rate of pressure changeduring the vacuum process is matched between the chambers.
 27. Theapparatus as claimed in claim 24 wherein the multi chambered systemcomprises a plurality of chambers contained on a same frame.
 28. Theapparatus as claimed in claim 24 wherein the multi chambered systemcomprises a plurality of chambers contained on separate pieces ofequipment.
 29. An apparatus for controlling a rate of pressure change ina vacuum process chamber during a vent up cycle of a vacuum processcomprising: a pressure sensor configured to sense a pressure within thechamber; a control valve in flow communication with the chamber and withan inert gas supply; and a controller for the control valve, saidcontroller in electrical communication with the sensor, said controllerconfigured to control flow from the gas supply through the control valveto the chamber, said controller responsive to input from the sensor toachieve a desired rate of pressure change in the chamber.
 30. Theapparatus as claimed in claim 29 wherein the controller comprises aprogrammable memory wherein the desired rate of pressure change isstored.
 31. The apparatus as claimed in claim 29 wherein the chamber ispart of a multi chambered system and the rate of pressure change duringthe vacuum process is matched between the chambers.
 32. An apparatus forcontrolling a vacuum process in a process chamber comprising: a pressuresensor configured to sense a pressure within the chamber; a flow controlvalve in flow communication with the chamber; and a controller for thecontrol valve in electrical communication with the sensor, saidcontroller programmable with a desired rate of pressure change for thevacuum process, said controller configured to adjust a position of thecontrol valve responsive to the pressure to achieve the desired rate ofpressure change in the chamber during the vacuum process.
 33. Theapparatus as claimed in claim 32 wherein the vacuum process comprises apump down cycle wherein the chamber is evacuated to an operatingpressure.
 34. The apparatus as claimed in claim 32 wherein the vacuumprocess comprises a vent up cycle wherein the chamber is pressurized.35. The apparatus as claimed in claim 32 wherein the control valve is inflow communication with a vacuum pump.
 36. The apparatus as claimed inclaim 32 wherein the control valve is in flow communication with a gassupply.
 37. A vacuum system comprising: a first process chamber and asecond process chamber; a first pressure sensor in the first processchamber and a second pressure sensor in the second process chamber; anda controller coupled to the first and second pressure sensors configuredto control flow rates from the first and second chambers such that arate of pressure change in the first and second chambers during a vacuumprocess matches.
 38. The system as claimed in claim 37 wherein thevacuum process includes a pump down cycle and the controller causes theprocess chambers to have matching rates of pressure change during thepump down cycle.
 39. A vacuum system comprising: a first process chamberand a second process chamber; a first pressure sensor in the firstprocess chamber and a second pressure sensor in the second processchamber; and a first controller coupled to the first pressure sensor; asecond controller coupled to the second pressure sensor; said first andsecond controllers configured to control flow rates into the first andsecond chambers such that a rate of pressure change in the first andsecond chambers during a vacuum process matches.
 40. The system asclaimed in claim 39 wherein the vacuum process includes a vent up cycleand the first and second controllers cause the first and second processchambers to have matching rates of pressure change during the vent upcycle.
 41. The system as claimed in claim 39 wherein the first andsecond process chambers are contained on a same frame.
 42. The system asclaimed in claim 39 wherein the first and second process chambers arecontained on separate pieces of equipment.
 43. A system for controllingpressure for a plurality of vacuum processes comprising: a first processchamber and a second process chamber; a first pressure sensor in thefirst process chamber and a second pressure sensor in the second processchamber; a first control valve in flow communication with the firstprocess chamber and a second control valve in flow communication withthe second process chamber; and a first controller coupled to the firstcontrol valve and first pressure sensor, and a second controller coupledto the second control valve and the second pressure sensor, saidcontrollers responsive to the sensors to match a rate of pressure changein the first and second process chambers during the vacuum processes.44. The system as claimed in claim 43 wherein the controllers areprogrammable with a desired rate of pressure change.
 45. The system asclaimed in claim 43 wherein the vacuum processes include a pump downcycle and a vent up cycle.
 46. The system as claimed in claim 43 whereinthe vacuum processes comprises a deposition or etching process.
 47. Thesystem as claimed in claim 43 wherein the first process chamber and thesecond process chamber are contained on a same frame.
 48. The system asclaimed in claim 43 wherein the first process chamber and the secondprocess chamber are contained on separate pieces of equipment.
 49. Avacuum system for semiconductor wafers comprising: a wafer handlerconfigured to transport the wafers; a plurality of vacuum processchambers configured to receive wafers from the wafer handler; a pressuresensor in each process chamber; a flow control valve associated witheach chamber for controlling a flow rate into or out of each chamber;and a controller for controlling each control valve, said controllersconfigured to control the control valves such that a rate of pressurechange in the chambers during a vacuum process substantially matches adesired rate of pressure change.
 50. The system as claimed in claim 49wherein the flow control valves are in flow communication withevacuation pumps for a pump down cycle.
 51. The system as claimed inclaim 49 wherein the flow control valves are in flow communication withan inert gas supply for a vent up cycle.
 52. A vacuum system forsemiconductor wafers comprising: a first process chamber and a secondprocess chamber configured to perform a same vacuum process; a firstpressure sensor for sensing pressure in the first process chamber and asecond pressure sensor for sensing pressure in the second processchamber; a first control valve for controlling a first flow rate fromthe first process chamber and a second control valve for controlling asecond flow rate from the second process chamber; a first controllerresponsive to the first pressure sensor for controlling the first flowrate and a second controller responsive to the second pressure sensorfor controlling the second flow rate; wherein said first and secondcontrollers are programmed such that the first and second flow ratescomprise substantially a same value.
 53. The vacuum system as claimed inclaim 52 wherein the first process chamber and the second processchamber are contained on a same frame.
 54. The vacuum system as claimedin claim 52 wherein the first process chamber and the second processchamber are contained on separate pieces of equipment.
 55. The vacuumsystem as claimed in claim 52 wherein the same vacuum process comprisesa deposition process.
 56. The vacuum system as claimed in claim 52wherein the same vacuum process comprises an etching process.